The present invention generally relates to a method for pre-treating process streams for use by thermal oxidizers. More specifically, the invention relates to a method for treating condensibles in such process streams.
Thermal oxidizers are sometimes required to process gas streams containing condensible compounds, which may be either organic or inorganic compounds. For example, pollutant streams containing volatile organic compounds (VOCs) from paint or other facilities may require cleaning prior to exhaust to the environment. Such thermal oxidizers include regenerative thermal oxidizers, recuperative thermal oxidizers, catalytic oxidizers and regenerative catalytic oxidizers. All of these oxidizers will be generically referred to here as "thermal oxidizers", and the principles of the present invention can be used with each type of oxidizer.
If condensible compounds within the process stream are permitted to collect as a liquid or solid in the process duct or in the thermal oxidizer, the oxidizer may run inefficiently or malfunction, and pluggages or fires can result. Also, if the compound is allowed to condense, the resulting liquid or particulant may become a pollutant that is difficult to cleanse. Thus, it is generally desirable to incinerate compounds in their gaseous state. This invention relates to methods for preventing this condensation from occurring when using thermal oxidizers.
Known prior art thermal oxidizers employ auxiliary heating (i.e., heating methods not using the thermal oxidizer itself) to prevent condensation of organic or inorganic compounds. This is inefficient, since heat from outside the system must be employed.
Alternatively, known prior art thermal oxidizers remove or trap condensibles by, for example, washing them out. This is also not desirable since it requires additional equipment and results in subsidiary waste streams which must also be treated.
It would therefore be advantageous to provide a more reliable and efficient thermal oxidizer which would eliminate or reduce the condensation of organic compounds with a process stream without relying solely upon auxiliary heat, and without generating additional waste streams.
It would also be advantageous to provide a system which both prevents the condensation of VOC's and properly oxidizes intermittent high-VOC-concentration process streams. Currently available thermal oxidizer configurations require by-pass hardware when encountering such process streams. This results in a greater loss of thermal energy to the exhaust stack and greater capital costs (i.e., larger and more expensive blowers or fans). Also, previous designs for regenerative thermal oxidizers required the use of additional preheating hardware as well as a hot damper and by-pass duct work for the high temperature control system used to handle higher VOC concentrations. Alternatively, it would be desirable to employ a treatment system for intermittent high-VOC-concentration process streams which operates independently of a condensation minimization system.